title: Effect of estrogen on tendon collagen synthesis, tendon structural characteristics, and biomechanical properties in postmenopausal women.
abstract: The knowledge about the effect of estradiol on tendon connective tissue is limited. Therefore, we studied the influence of estradiol on tendon synthesis, structure, and biomechanical properties in postmenopausal women. Nonusers (control, n = 10) or habitual users of oral estradiol replacement therapy (ERT, n = 10) were studied at rest and in response to one-legged resistance exercise. Synthesis of tendon collagen was determined by stable isotope incorporation [fractional synthesis rate (FSR)] and microdialysis technique (NH(2)-terminal propeptide of type I collagen synthesis). Tendon area and fibril characteristics were determined by MRI and transmission electron microscopy, whereas tendon biomechanical properties were measured during isometric maximal voluntary contraction by ultrasound recording. Tendon FSR was markedly higher in ERT users (P < 0.001), whereas no group difference was seen in tendon NH(2)-terminal propeptide of type I collagen synthesis (P = 0.32). In ERT users, positive correlations between serum estradiol (s-estradiol) and tendon synthesis were observed, whereas change in tendon synthesis from rest to exercise was negatively correlated to s-estradiol. Tendon area, fibril density, fibril volume fraction, and fibril mean area did not differ between groups. However, the percentage of medium-sized fibrils was higher in ERT users (P < 0.05), whereas the percentage of large fibrils tended to be greater in control (P = 0.10). A lower Young's modulus (GPa/%) was found in ERT users (P < 0.05). In conclusion, estradiol administration was associated with higher tendon FSR and a higher relative number of smaller fibrils. Whereas this indicates stimulated collagen turnover in the resting state, collagen responses to exercise were negatively associated with s-estradiol. These results indicate a pivotal role for estradiol in maintaining homeostasis of female connective tissue.
authors.affiliation: Institute of Sports Medicine, Bispebjerg Hospital, and Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark. kontakt@mettehansen.nu
authors.forename: Mette
authors.initials: M
authors.lastname: Hansen
authors.forename: Mads
authors.initials: M
authors.lastname: Kongsgaard
authors.forename: Lars
authors.initials: L
authors.lastname: Holm
authors.forename: Dorthe
authors.initials: D
authors.lastname: Skovgaard
authors.forename: S Peter
authors.initials: SP
authors.lastname: Magnusson
authors.forename: Klaus
authors.initials: K
authors.lastname: Qvortrup
authors.forename: Jytte O
authors.initials: JO
authors.lastname: Larsen
authors.forename: Per
authors.initials: P
authors.lastname: Aagaard
authors.forename: Morten
authors.initials: M
authors.lastname: Dahl
authors.forename: Annette
authors.initials: A
authors.lastname: Serup
authors.forename: Jan
authors.initials: J
authors.lastname: Frystyk
authors.forename: Allan
authors.initials: A
authors.lastname: Flyvbjerg
authors.forename: Henning
authors.initials: H
authors.lastname: Langberg
authors.forename: Michael
authors.initials: M
authors.lastname: Kjaer
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism; D003094:Collagen / Q000096:biosynthesis*; D003430:Cross-Sectional Studies; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000096:biosynthesis; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis; D017551:Microdialysis; D046529:Microscopy, Electron, Transmission; D008875:Middle Aged; D017847:Patellar Ligament / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism; D017698:Postmenopause / Q000502:physiology*; D011392:Proline / Q000097:blood; D013710:Tendons / Q000033:anatomy & histology* / Q000187:drug effects / Q000378:metabolism*
chemical_list: D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D003094:Collagen; D011392:Proline